In recent years, semiconductor laser devices, semiconductor devices and so on have been used in various fields. Since such devices have large heat release values, heat sinks are generally used for cooling these devices.
Heat sinks are required to have even higher cooling performance responsive to the high intensity and high output of semiconductor devices, etc. in recent years. They are also required to show durability, etc. so as to be capable of cooling the semiconductor devices, etc. stably for long periods. Thus, wide varieties of heat sinks have been devised.
Such heat sinks are showing a tendency toward increases in size and increases in sheet thickness in order to achieve enhanced performance. Thus, it has been desired that the heat sinks be adapted to semiconductor devices, etc. which have been increasingly downsized in recent years.
Under these circumstances, the structure of a water-cooled heat sink 51 (see JP-A-2005-093781) is disclosed.
FIG. 5 is a sectional view of the water-cooled heat sink 51, and FIG. 6 is an exploded sectional view of the water-cooled heat sink 51.
The heat sink 51 has three plate-shaped base materials, i.e., an upper plate material 52, an intermediate plate material 53, and a lower plate material 54. The upper plate material 52 and the lower plate material 54 each have a concave cross-sectional shape, while the intermediate member 53 is in the form of a flat plate. Cu which is a material having excellent heat conductivity is used as the material for these plate materials. The upper plate material 52 is joined onto the intermediate plate material 53 via a solder layer 55, and an upper flow path 56 is formed between the plate materials 52 and 53. The lower plate material 54 is joined to a lower portion of the intermediate plate material 53 via a solder layer 57, and a lower flow path 58 is formed between the plate materials 53 and 54. A through-hole 59 providing communication between the upper and lower flow paths 56 and 58 is formed in the intermediate plate material 53. An outlet 60 for cooling water is formed in the lower plate material 54, and an inlet 61 for cooling water is formed in the upper plate material 52. A semiconductor device 62 cooled by the heat sink 51 is joined to the surface of the upper plate material 52 via a solder layer 63.
The heat sink 51 has a feed water pump (not shown) connected between the inlet 61 and the outlet 60 outside the heat sink 51 so that cooling water flows through the inlet 61, the upper flow path 56, the through-hole 59, the lower flow path 58, and the outlet 60 in this sequence, whereby the heat sink 51 can absorb heat generated by the semiconductor device 62.
The heat sink 51 of the above configuration is constructed by joining in the following manner:
The plate materials 52 to 54 as base materials are readied for use. The upper and lower flow paths 56, 58, the through-hole 59, the inlet 61 and the outlet 60 are formed using a method, for example, a processing method such as cutting, a forming method such as casting or forging, or a surface treatment method such as etching.
As a treatment before joining of the plate materials 52 to 54, it is preferred to perform plasma treatment, in which an inert gas or the like is excited in a vacuum to convert it into a plasmatized state with high reactivity, and the plasma is brought into contact with coating layers, thereby cleaning the surfaces of the respective layers to be joined. By so doing, contaminants which inhibit diffusion joining are removed. The removal of the contaminants may be carried out by other cleaning method such as wet treatment.
The surface of each of the plate materials 52 to 54 cleaned by plasma treatment is coated with a Ni coating layer (not shown), and a Au coating layer (not shown) is coated on the Ni coating layer. Then, the solder layers 55, 57 each of a Au—Sn alloy solder or a pure Sn solder are interposed between the surfaces of the plate materials 52 to 54 to be joined.
The Ni coating layer is used as an adhesive layer coated between any of the plate materials 52 to 54 and the Au coating layer. The Au coating has high corrosion resistance, and is used for preventing corrosion, erosion-corrosion, or electrolytic corrosion which occurs in the heat sink. The joining of the plate materials 52 to 54 by the solder layers 55 and 57 is preferably performed in a reducing atmosphere, or a non-oxidizing atmosphere such as a nitrogen gas or an argon gas, or in a vacuum.
The above-described water-cooled heat sink has excellent heat absorbing properties, but is formed by joining (laminating) the plate material shaving flow paths formed therein, and may be small in size. When the water-cooled heat sink is used under pressure, it may be damaged, if its joint or joining area is not complete.
The present invention has been accomplished in the light of the above-described situations. It is an object of the invention to provide a method of producing a body having a flow path formed therein, the body having an integrated structure, and having inside a precise, freely formed flow path, the body being produced without using a technique for pasting or laminating a plurality of metal sheets; and a water-cooled heat sink produced by the method.